Abstract: A method of displaying a defect appearing on an elongated object conveyed in one direction. The method comprises the steps of scanning the object in the width direction thereof by means of a sensor camera, and obtaining object image data corresponding to the object, processing the object image data, to detect a defect in the object, storing the object image data in an image memory in a scroll manner, stopping the scroll storing of the object image data in the image memory and storing the object image data output subsequently from the sensor camera in the other image memory in response to the detection of the defect, and retaining the object image data including the defect in the image memories as still image data, and displaying the still image data read out from the image memories on a monitor screen as a still image such that the defect is displayed at a predetermined position on the monitor screen.

Abstract: In detecting surface defects of a hot metal body, e.g. hot-rolled steel sheet, by using a first video signal derived from radiation spontaneously radiated from a target area of the hot metal surface and a second video signal derived from external light projected on and reflected from the same target area of the hot metal surface, the rate of false detection by the influence of noise signals attributed to metal oxide present on the hot metal surface is greatly reduced by converting the first and second video signals respectively into first and second binary signals, synchronously feeding the first and second binary signals to an AND circuit and detecting the locations of such defects based on the output of the AND circuit. Preferably near-infrared region of the radiation is used in producing the first video signal and visible light as the external light.

Abstract: A method and apparatus for examining the surface condition of a traveling metal strip in the process of being continuously cast for detection of scarfs, if any, produced on said surface, wherein a light emitter projects light beams of short waves or those containing said short waves and other waves on a traveling metal strip in the process of being continuously cast; among the reflections of the projected light beams, only those consisting of short waves are received by the light detector through a filter; a flat hood surrounding a light path extending between the light emitter and light detector is set in a cooling chamber; compressed air streams run through the flat hood to air purge or clean the environment of the light path; a signal issued from the light detector is processed by an image memory; the shade image of the traveling metal strip is continuously displayed on the screen of a monitor television set; and the surface condition of the traveling metal strip is examined on the screen to detect scarfs,